In automatic welding, the aim is to guide the welding torch accurately along the joint. Such a result is presently achieved by forcibly guiding the welding torch or the complete welding units along the joint utilizing mechanical or optical elements, such as guide rolls or photosensors. In such cases, however, the feelers or guide elements must be mounted a safe distance from the arc so that their ability to function is not disadvantageously affected by the side effects of the arc, such as heat and light. Problems can also be caused in such processes by welding spatter, non-uniform seam preparation, binding sites, etc.
Such a process is thus described in U.S. Pat. No. 3,204,081. In that process, the arc is deflected continuously and periodically at right angles to the joint and over the surfaces of the neighboring two workpieces. On crossing the joint, recurring voltage and current impulses are produced periodically, which are employed for the control. At the same time, however, the arc is thereby moved over surfaces of the workpiece which lie outside of the area of the welded joint. The conditions of these surfaces are therefore unfavorably affected by the arc.